1. Field of the Invention
This invention relates in general to computer systems and, more particularly, to computer systems which are designed to partially power down or suspend operation when left unattended.
2. Description of Related Art
Personal computer systems in general and IBM compatible personal computer systems in particular have attained widespread use. These personal computer systems now provide computing power to many segments of today's modern society. A personal computer system can usually be defined as a desktop, floor-standing, or portable microcomputer that includes a system unit having a system processor with associated volatile and non-volatile memory, a display monitor, a keyboard, one or more floppy diskette drives, a hard disk storage device and an optional printer. One of the distinguishing characteristics of these systems is the use of a system board or motherboard to electrically connect these components together. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses.
Portable computers are often referred to as laptop, notebook or subnotebook computers. These computers typically incorporate a flat panel display such as a liquid crystal display (LCD) or other relatively small display. Generally, the panel display is incorporated into the lid of the computer which can be opened for use or closed for storage. Portable computers also often provide for coupling to a conventional standalone display monitor.
To be truly portable, these computers require a portable energy source such as an internal battery for example. The power demands placed on such an internal battery even in the best designed computer systems can be very substantial. The ever increasing performance of the microprocessors employed in today's portable computers corresponds to a similar increase in the power demands on the internal battery. At the same time, users desire relatively lightweight portable computers. The need for size and weight reduction in portable computers places a practical limit on the size of the internal battery used in the portable computer. Clearly, it is essential to be very efficient in the use of power which is supplied by the internal battery of the portable computer.
One known technique of power management to achieve battery conservation in a portable computer is to power down the machine when the user closes the lid of the computer. Another technique is to provide the user with a dedicated key combination or button ("hot key") which when activated sends the portable computer into a partially powered down or "suspend state" in which less energy is being consumed. For example, in such a "suspend state", the hard drive and/or panel display can be turned off to conserve power. The states of circuits internal to the computer are stored so that they can be later restored when operation resumes. In one approach, by simply entering a keystroke the computer resumes operation at the same point in the application where the user went into the suspend state. A modest time penalty is paid however by the user since a few seconds are required to power up the panel display and the hard drive and to restore the internal circuitry of the computer to former states before operation resumes. The above described power management approach is a form of suspend-resume operation which is manually activated by the user.
In a more advanced suspend-resume approach, it is possible for the suspend state to be automatically activated after a time period of no user activity has transpired. For example, if the lid is open and the user has keyed no characters into the keyboard in over 10 minutes, then the suspend mode is automatically entered. Many computers permit the user to select the duration of this timeout time period. Generally, users select this timeout time period to be a relatively long amount of time such as 10 minutes or more to avoid the frustration of the computer constantly powering down when the user pauses for thought or other activity.
Portable computer users desire both power conservation and computer availability. Unfortunately, these goals are in conflict. If the portable computer is fully powered up and ready for use at all times, then power conservation is at a minimum. In contrast, if the portable computer is nearly always in suspend mode, it is not available for immediate usage most of the time.
Current power management schemes either don't sustain activity when the lid is closed or fail to more aggressively conserve power. The increased use of portable computers as general purpose communicators increases the need for user unattended machines to be responsive when messages arrive at the computer through wireless communication devices or modems. It is noted that in some portable computers, closing the lid either forces an immediately suspend operation or the portable computer simply continues as if it were in use by the user. In the scenario where closing the lid forces an immediate suspend operation, the system can resume operation for communication or clock events. However, should even a relatively short duration gap occur in the communication event or stream, the system immediately returns to suspend mode and valuable data can be lost.